Yellow jack

Species of fish

The yellow jack (Carangoides bartholomaei), also known as coolihoo, is a species of marine fish in the jack family, Carangidae. It is one of only two representatives of its genus present in the Atlantic Ocean, inhabiting waters off the east coast of the Americas from Massachusetts in the north to Brazil in the south, as well as a number of offshore islands. The yellow jack can be distinguished from closely related species by the length of the jaw, as well as counts of the rays in the fins. It is a fairly large fish, growing to a recorded maximum length of , and a weight of at least Yellow jack inhabit reefs, moving either individually or in schools and are predatory fish which primarily take other small fish. Studies in the Caribbean suggest the species reaches sexual maturity between , and spawns in offshore waters from February to October. Yellow jack are of minor economic importance, taken by both hook and net methods, and are considered to be fair table fish. They are often caught by boat anglers, although are overlooked for their larger relatives.

The yellow jack is classified within the genus Carangoides, a group of fish commonly called jacks and trevallies. Carangoides falls into the jack and horse mackerel family Carangidae, the Carangidae are part of the order Carangiformes. The species was first scientifically described by the famed French taxonomist Georges Cuvier in 1833, based on the holotype specimen collected from St. Bartholomew Island in the West Indies. Cuvier named this new species Caranx bartholomaei after the island from which the holotype was taken. The genus in which the taxon should be placed has proved contentious, and continues to be today with a number of recent publications placing the species in Carangoides, while others still classify it within Caranx. This article follows the Fishbase and ITIS classification of Carangoides bartholomaei. The species predominant common name, "yellow jack", comes from the colour the species turns as it gets older, with other common names including "coolihoo" and incorrectly, "green jack". Some authorities place the yellow jack in the genus Caranx.

The yellow jack shows the typical body profile of the genus Carangoides, having a moderately deep, compressed elongate shape, with the dorsal profile slightly more convex than the ventral profile.

Yellow jack are predatory fish, moving both individually or in small groups, with their main prey being small fish, In one case, they were observed following a flying gurnard, itself smaller than the jack, that disturbed the substrate, causing various organisms to be displaced and become available for predation. Yellow jacks reach maturity at different times in different locations, with studies around Cuba showing males reach sexual maturity at and females at , while in Jamaica, males reach sexual maturity at Spawning takes place in offshore waters between February and October. Juveniles live near the surface of the ocean, often hiding amongst large mats of jellyfish or Sargassum weed, with a coloration that camouflages the fish in the weed. These young fish are often moved long distances by the Gulf Stream, and this is probably the process responsible for fish found as far north as Massachusetts.

Yellow jack are a minor commercial species throughout their range, taken by seines, trawls and hook and line techniques. They are also caught by recreational fishermen, with fish baits and lures and often while trolling, although they are rarely targeted specifically. The species is rated as a fair to good table fish, and is marketed both fresh and salted. The yellow jack was actually the first species outside of the Pacific Ocean to be confirmed as carrying ciguatera toxins, although these early studies showed that the toxin was biochemically slightly different from the Pacific strain.